The invention relates to marine fuel distribution systems, and more particularly to marine fuel distribution systems including a fuel tank inside a boat, and means for supplying fuel from the fuel tank to the engine of a marine propulsion device mounted on the boat.
Present fuel distribution systems typically include a fuel pump mounted on and driven by the engine of the marine propulsion device, and a fuel supply line communicating between a fuel tank and the suction side of the fuel pump. Other components, such as an anti-siphon valve, a tank switching valve, and an in-line fuel filter, may be included on the suction side of the fuel pump. The fuel pump must create a negative pressure to draw fuel through the fuel distribution system, and this negative pressure can cause the fuel to vaporize in the fuel supply line. The result can be inability of the fuel distribution system to supply liquid fuel to the engine at a given fuel flow rate due to excessive fuel vapor generation, often referred to as vapor lock.
The only known method of preventing vapor lock is to pump the fuel under pressure through the fuel distribution system to the engine. Pumping the fuel under pressure will eliminate the tendency of the fuel to vaporize because it is at a positive pressure. However, leakage of a pressurized fuel line would allow fuel to leak into the bilge of a boat.
Attention is directed to Ellis U.S. Pat. No. 4,416,638, issued Nov. 22, 1983, which discloses a fuel distribution system including a casing surrounding the upstream portion of a gas feed pipe between the boat transom and the carburetor of the engine. The casing is not connected to the source of fuel and does not surround the entire portion of the fuel pipe located interiorly of the boat.
Attention is also directed to the following U.S. patents which disclose fuel distribution systems: Lee U.S. Pat. No. 741,512, issued Oct. 13, 1903, Butler U.S. Pat. No. 1,724,559, issued Aug. 13, 1929, Wise U.S. Pat. No. 3,031,010, issued Apr. 24, 1962, Gauck U.S. Pat. No. 3,696,799, issued Oct. 10, 1972, Heath U.S. Pat. No. 3,957,025, issued May 18, 1976, Weissenbach U.S. Pat. No. 3,977,379, issued Aug. 31, 1976, Lee U.S. Pat. No. 4,136,652, issued Jan. 30, 1979, Stolz U.S. Pat. No. 4,285,316, issued Aug. 25, 1981 and Robinson U.S. Pat. No. 4,362,130, issued Dec. 7, 1982.